Vacuum cleaners serve to pick up a wide array of materials. Aside from vacuum cleaners for dry materials, there are also vacuum cleaners for picking up liquids. Such vacuum cleaners are normally referred to as wet/dry vacuum cleaners.
Vacuum cleaners have, for example, a fan or a suction turbine as the source of negative pressure to generate an air stream that follows a flow path in the housing. Air is drawn into the housing by the negative-pressure source, for example, through a suction hose arranged at a suction opening of the housing, and subsequently blown out of the housing via a discharge opening provided on the housing at a distance from the suction opening. The area of the flow path between the suction opening and the negative-pressure source is referred to as the suction side of the vacuum cleaner. The area of the flow path between the negative-pressure source and the discharge opening is referred to as the excess-pressure side of the vacuum cleaner. In order to protect the negative-pressure source as well as the surroundings from particles that are transported along with the air stream, normally at least one filter element is provided upstream from the negative-pressure source, thus on the suction side of the negative-pressure source.
U.S. Pat. Appl. No. 2010/0139032 A1 discloses a vacuum cleaner having a housing, a filter element for separating out particles that have been picked up and transported in an air stream as well as a holding device for holding the filter element in the housing. The filter element has a projecting holding section. The holding device comprises a housing which surrounds the filter element and through which an air stream flows and it also comprises a contact surface and a holding surface between which the holding section of the filter element comes to rest when the filter element is in the installed state.